if you had a square template that was 7 1/2 it would be easy. What I do is to trim an 1/8 off of one side and rotate and put cut line on the 7 7/8 mark on your cutting mat. then trim the opposite side. after doing both sides I rotate it once more. Then I would put that cut line on a horizontal line and keep it squared with the top, then take 1/4 in. slice off of the other 2 sides now. now with that done rotate to the side you 1st cut and trim off the last 8/th